The present invention involves a method for determining an azimuth and/or elevation angle, in which a radar target is located relative to a reference system, and to a radar system based on this. The radar system itself preferably serves as the reference system. Known methods for angle determination are described for instance in "Radar Handbook" by M. Skolnik.
One widely used option is accordingly the use of an antenna with an antenna lobe sharply focused in the plane of the angle sought; the lobe is swiveled mechanically for observing or measuring an angular range. From the position of the antenna at the moment when the reflection of a radar target is received, the angle of the radar target can be determined. A disadvantage of this method is the mechanical rotation of the antenna, which on the one hand involves mechanical wear and on the other takes a comparatively long time because of the inertia of the masses moved. To avoid these disadvantages, a phased array antenna can be used, in which the associated antenna lobe is swiveled electronically. However, this requires of a sharp focusing of many active, phase-controlled transmission/reception elements, which in turn requires comparatively major effort and expense to achieve. It is moreover common to both methods that the observed angular range is scanned sequentially. Depending on the scanning speed, this can worsen the accuracy of the angle measurement.
Another principle for angle determination, also described by Skolnik, is known as the monopulse method. It uses an antenna that has at least two only partly overlapping antenna lobes, located in the plane of the angle sought. The reflections of the detected radar target are now received via each of the at least two antenna lobes. For determining the angle, in the so-called phase monopulse the phase difference among the received reflections from all the antenna lobes is evaluated. In the so-called amplitude monopulse, one differential signal and one summation signal each is formed from the reflections received via the individual antenna lobes. The quotient of the two signals depends approximately linearly on the angle of the radar target detected. A disadvantage of both variants of the monopulse method, however, is that the determined angle of a radar target is unequivocal only within existing limits. Reflections from radar targets that are located outside the unequivocal angular range are misinterpreted in this method. Moreover, the amplitude monopulse method particularly requires approximately identical antenna lobes arranged symmetrically to one another. This in turn means comparatively major effort and expense for producing and maintaining the antenna.